Privacy & how it works

FunctionForge on the web is built the same way as our iOS apps: private by design.

Everything stays on this device

Your progress — best scores and XP — is stored only in this browser (on-device storage). It is never sent anywhere. Clear your browser data and it's gone; nobody else can see it.

No accounts, no ads, no tracking

There is no sign-up and no login. There are no ads and no in-app purchases. There are no third-party trackers embedded in the app.

How it works

Feed numbers through a function machine and watch what comes out — predict outputs, work backwards to find inputs, chain two machines, or crack a machine's hidden rule from the input-output pairs. On the Graph Plotter, build y = mx + b to match a target line, read the slope and intercept off a graph, and try the vertical line test. Or run a Concepts kit: a short round of questions. A hint appears only after a first try, so you think it through first — and mistakes are treated as part of learning.

Built for ages 9–14

The 400 Concepts questions come straight from the FunctionForge iOS app and are aligned to Common Core standards for functions, expressions, and equations (grades 4–8). Everything works with the sound off and can be played entirely by keyboard.

Spark & Anvil is a 501(c)(3) public charity. Apps stay free forever. This page is a plain-language summary, not legal advice.

Full parent guide Site privacy policy